The p21 proteins encoded by the ras genes of Harvey and Kirsten murine sarcoma viruses are directly responsible for the initiation and maintenance of virus-induced malilgnant transformation of the infected cells. This project seeks to characterize the p21 ras, to investigate the interaction of this protein with cellular components, and to study the structure-function relationship of this protein as a step to understand the biochemical pathway leading to conversion of normal cells into cancer cells. Large quantities of the Ha-p21 have been produced in E. coli in order to undertake detailed protein biochemistry studies. The biosynthesis of the p21 ras encoded by the EJ bladder ras gene has been studied. Structure-function relationship studies using the synthetic peptide and genetic engineering approaches have been undertaken. The hormonal responsiveness of the Ha-MuSV transformed cells was also investigated.